Porcelain Pottery

does anyone know.....?

how to identify the makers ''mark'' on a piece of porcelain/pottery.I have a ''face'' plaque of a young lady's head.On the back[stamped] is a crown and below it are the letters W and G[or maybe C] on top of each other.

Check out two sources: http://www.antique-china-porcelain-collectibles.com/porcelain_mark.htm
http://www.pottery-english.com/ where one finds Pottery Marks, on the list on the left side